Internal mold release agent for use in reaction injection molding

ABSTRACT

The present invention is directed to a process for the production of optionally cellular, polyurethane elastomer molding by reacting a reaction mixture containing 
     (I) a polyisocyanate, 
     (II) an isocyanate-reactive polymer having a molecular weight of about 1800 to 12,000, 
     (III) about 5 to 50% by weight, based on the weight of component (II) of a chain extender comprising a sterically hindered aromatic diamine and 
     (IV) an internal mold release agent mixture comprising 
     (a) about 0.5 to 10% by weight, based on the weight of components (II) and (III) of a zinc carboxylate containing 8 to 24 carbon atoms per carboxylate group and 
     (b) a compatibilizer comprising a member selected from the group consisting of nitrogen-containing, isocyanate-reactive, acyclic compounds and nitrogen-containing, isocyanate-reactive polymers in an amount sufficient to solubilize the zinc carboxylate so that when the internal mold release agent mixture is in admixture with components (II) and (III), the zinc carboxylate possesses improved resistance to precipitation, 
     the reaction mixture being processed as a one-shot system by the RIM process at an isocyanate index of about 70 to 130.

This is a continuation of application Ser. No. 643,612 filed Aug. 23,1984, and now U.S. Pat. No. 4,519,965.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a RIM process using a moldingcomposition which contains an internal mold release agent mixture basedon a zinc carboxylate and a compatibilizer.

2. Description of the Prior Art

Reaction injection molding (RIM) has become an important process for thefabrication for external automotive body parts and other industrialthermoset moldings. The RIM process is a so-called "one-shot" processwhich entails the intimate mixing of a polyisocyanate component and anisocyanate-reactive component followed by the injection of thisadmixture into a mold for subsequent rapid curing. The polyisocyanatecomponent is generally based on a liquid polyisocyanate. Theisocyanate-reactive component contains a high molecular weightisocyanate-reactive component, usually a polyol, and optionally a chainextender containing amino or hydroxyl groups. U.S. Pat. No. 4,269,945discloses a specific chain extender which contains an aliphaticamine-containing compound having at least one primary amino group suchas an aminated polyoxypropylene glycol, and either a hydroxyl-containingcompound free of aliphatic amine hydrogen atoms or an aromatic aminehydrogen-containing compound which is free of aliphatic amine. U.S. Pat.No. 4,218,543 discloses a chain extender which is miscible with thepolyol component and is based on compounds containing stericallyhindered amino groups such as 1-methyl-3,5-diethyl-2,4-diamino benzene,1-methyl-3,5-diethyl-2,6-diamino benzene or mixtures thereof.

While products produced by the RIM process have excellent physicalproperties, the use of the RIM process has been limited by the necessityto spray external mold release agents (waxes, soaps, etc.) onto the moldsurface before each shot or every several shots. Molding without such anexternal release agent results, using standard molding compositions, inparts that are torn, distorted or otherwise damaged because of theadhesion of the molded part to the mold surface. Several attempts havebeen made to formulate reaction components which contain an internalmold release agent so that the need to repeatedly apply external moldrelease agents to the mold surface would either be eliminated ordiminished.

U.S. Pat. No. 4,379,100 is directed to the use of apolycarboxy-functional alkyl siloxane as an internal release agent;however, this internal release agent is not preblended with either thepolyisocyanate or polyol component, but rather is introduced as a thirdstream to the mixhead of the injection apparatus. U.S. Pat. No.4,076,695 is also directed to the use of a carboxy-functional siloxanewhich may be incorporated with either a polyisocyanate or polyolcomponent as an internal mold release agent. A third patent directed tothe use of carboxy-functional silanes is U.S. Pat. No. 4,396,729.However, it is disclosed therein that amino-functional reactants arenecessary since polyol reactants require the use of a tin catalyst whichinteracts with the carboxy groups of the release agent resulting ininferior products. U.S. Pat. No. 4,374,222 is directed to the use ofhydroxyl-substituted fatty acid amides as an internal mold release agentfor use in the RIM process.

The use of metallic carboxylic acid salts as an internal mold releaseagent for various systems has also been disclosed. For example, U.S.Pat. No. 4,067,845 is directed to molded unsaturated polyester resinsystems utilizing a dual thickening system based on a metallic oxide anda polyisocyanate and, in addition, a mold release agent based on zincstearate. British Pat. No. 2,101,140 is directed to an internal moldrelease agent based on a metallic carboxylic salt such as zinc stearateand an epoxidized vegetable oil such as epoxidized soybean oil for usein a RIM process.

The use of zinc stearate as a catalyst is disclosed in U.S. Pat. No.4,119,594, wherein a mixture of solid particles of hydroquinonedi-(beta-hydroxyethyl)ether (as chain extender) and zinc stearate (ascatalyst) are dispersed in a liquid mixture of a polyether polyol and aliquid form of diphenylmethane diisocyanate and subsequently reacted ina RIM process to produce thermoset polyurethanes.

British Pat. No. 1,476,997 discloses the use of metallic carboxylates assurface quality improvers for polyamides, while U.S. Pat. No. 3,705,860discloses the use of metallic carboxylates as antifoam agents for paintsor paper pulp compositions.

One object of the present invention is to provide RIM moldingcompositions which would eliminate or decrease the frequency ofapplication of an external mold release agent to the surface of a mold,thereby, providing higher productivity. A further object of theinvention is to provide such molding compositions without introducingdetrimental effects on the physical properties (e.g., heat sag, flexuralmodulus, tear strength or tensile strength), processing characteristics(e.g., demold time, toughness at demold known as "green strength" orflowability), or post-molding operations, especially paintability.

It has been discovered that the objects of this invention can berealized by the modification of RIM molding compositions with theinternal mold release agent mixtures hereinafter described.

SUMMARY OF THE INVENTION

The present invention is directed to a process for the production ofoptionally cellular, polyurethane elastomer moldings by reacting areaction mixture containing

(I) a polyisocyanate,

(II) an isocyanate-reactive polymer having a molecular weight of about1800 to 12,000,

(III) about 5 to 50% by weight, based on the weight of component (II) ofa chain extender comprising a sterically hindered aromatic diamine and

(IV) an internal mold release agent mixture comprising

(a) about 0.5 to 10% by weight, based on the weight of components (II)and (III) of a zinc carboxylate containing 8 to 24 carbon atoms percarboxylate group and

(b) a compatibilizer comprising a member selected from the groupconsisting of nitrogen-containing, isocyanate-reactive, acycliccompounds and nitrogen-containing, isocyanate-reactive polymers in anamount sufficient to solubilize the zinc carboxylate so that when theinternal mold release agent mixture is in admixture with components (II)and (III), the zinc carboxylate possesses improved resistance toprecipitation,

the reaction mixture being processed as a one-shot system by the RIMprocess at an isocyanate index of about 70 to 130.

The present invention is also directed to an isocyanate-reactivecomponent for use in a RIM process based on components (II), (III) and(IV) and to an internal mold release agent mixture based on components(IV) and, optionally, (III).

DETAILED DESCRIPTION OF THE INVENTION

It has been observed that zinc carboxylates such as zinc stearate arenot effective as internal release agents in conventional polyurethaneRIM formulations based on polyisocyanates, high molecular weight polyolsand diamine chain extenders. The reason for this ineffectiveness is notcompletely understood, but may be because the zinc carboxylates areneither soluble in either the polyisocyanate or isocyanate-reactivecomponent, nor are the reaction mixtures processed at a sufficientlyhigh temperature for the salts to melt or dissolve. The key feature ofthe present invention is the discovery that compositions containing bothzinc carboxylates and sufficient amounts of the compatibilizersdiscussed hereinafter overcome the previous difficulties with regard tothe use of zinc carboxylates as internal mold release agents.Apparently, these specific additives assist in dissolving orcompatibilizing the zinc carboxylates in the isocyanate-reactivecomponent and/or reaction mixture and, thus, provide effective internalrelease performance without significantly affecting other properties,processing characteristics or paintability. Compositions containing onlyone component of the internal release agent mixture are ineffective ormuch less effective in providing internal release performance.

Zinc Carboxylates (IVa)

The suitable zinc carboxylates which may be used in the internal releaseagent mixture of the present invention are based on C₈ -C₂₄, branched orstraight chain fatty acids which may be saturated or unsaturated. Thecarboxylates also include the commercial preparations of a specificcarboxylate which also contains impurities or by-products of other fattyacid derivatives. For example, commercial "stearates" may also containsignificant quantities of palmitates, myristates, etc. and commercial"tall oil" derivatives normally contain mixtures of stearates,palmitates, oleates, etc. Examples of specific zinc carboxylates includezinc stearate, zinc oleate, zinc octoate, zinc laurate, zinc behenate,zinc ricinoleate and the like.

The preferred zinc carboxylates are those which remain soluble incombination with the compatibilizer when in admixture with the highmolecular weight isocyanate-reactive component (II) and the chainextender (III). The most preferred zinc carboxylate is zinc stearate,especially those having a high purity such as Zinc Stearate PolymerGrade Type N from Witco, Zinc Stearate RSN 131 HS and IPS fromMallinckrodt and Zinc Stearate Heat Stable Polymer Grade from Nuodex.The zinc carboxylates are used in amounts of about 0.5 to 10%,preferably about 1 to 6% and most preferably about 1 to 4%, by weight,based on the weight of components (II) and (III).

Compatibilizers (IVb)

Suitable compatibilizers are those which assist in compatibilizing orsolubilizing the zinc carboxylates in the resin blend and/or in thereaction mixture without substantially affecting the processingcharacteristics of the reaction mixture or the physical properties orpaintability of the molded articles produced therefrom. Thecompatibilizers include nitrogen-containing, isocyanate-reactive,acyclic compounds such as aliphatic polyamines and nitrogen-containing,isocyanate-reactive polymers, preferably polyethers. Preferredcompatibilizers include polyether polyamines and amine- orhydroxyl-terminated, amine-initiated polyethers (i.e., polyethersobtained by the addition of alkylene oxides such as ethylene oxideand/or propylene oxide to aromatic or aliphatic polyamines, optionallyfollowed by amination). Specific examples of these nitrogen-containing,isocyanate-reactive polymers include polyoxypropylene diamine (suppliedas Jeffamine D-230 from Texaco), polyoxypropylene diamine (supplied asJeffamine D-400 from Texaco), polyoxypropylene diamine (supplied asJeffamine D-2000 from Texaco), polyoxypropylene triamine (supplied asJeffamine T-403 from Texaco), polyoxypropylene triamine (supplied asJeffamine T-5000 from Texaco), an ethylene diamine-based polyetherpolyol (supplied as Multranol 4050 from Mobay) and a toluenediamine-based polyether polyol (supplied as Multranol 9136 from Mobay).

Even though any of the previously described compounds or polymers assistin compatibilizing or solubilizing the zinc carboxylates in the resinblend and/or in the reaction mixture, it has been found that the amine-or hydroxyl-terminated, amine-based polyethers provide long termstability of the zinc carboxylates, especially zinc stearates without agradual precipitation of the zinc stearates taking place. Theamine-based polyethers provide this increased storage stability whenthey are used as the sole compatibilizing or solubilizing agent or whenthey are used in combination with the nitrogen-containing,isocyanate-reactive, acyclic compounds or, especially, the polyetherpolyamines.

Preferred amine-based polyethers are those initiated with an aminecontaining at least two nitrogens and which contain the group--N--C--C--N--, i.e. wherein there are two carbons between thenitrogens. Examples of these amines include aliphatic amines such asethylene diamine, diethylene triamine, etc. and heterocyclic amines suchas piperazine or imidazolidine. Especially preferred are thealkoxylation products, preferably ethoxylation products and morepreferably the propoxylation products of ethylene diamine such as thepreviously described Multranol 4050.

The amount of the compatibilizer (IVb) is dependent upon many factorsincluding, but not limited to, the molecular weight of thecompatibilizer and, more specifically, the amount of nitrogen containedtherein. With regard to the low molecular weight compatibilizers havingmolecular weights of up to about 800, the amount to be used is about 0.5to 10.0%, preferably about 1 to 6% and most preferably about 1 to 4%, byweight, based on the weight of components (II) and (III). With regard tomedium molecular weight compatibilizers having molecular weights betweenabout 800 and 3,000, preferably between about 800 and 1,800, the amountto be used is about 2 to 30%, preferably about 4 to 20%, by weight,based on the weight of components (II) and (III).

While the use of large amounts of the compatibilizers do not have adetrimental effect on releasability, they may have detrimental effectson processing characteristics such as flow lines, density gradients andincomplete mold filling or on physical properties such as low elongationand part brittleness. These detrimental effects are more apparent whenthe compatibilizers are not suitable for use as the high molecularweight, isocyanate-reactive component (II), i.e. compatibilizers whichdo not have molecular weights of greater than about 1,800, preferablygreater than about 3,000.

It is also possible to use high molecular weight compatibilizers havingmolecular weights greater than about 1,800, preferably greater thanabout 3,000. These compatibilizers are used in amounts greater thanabout 4%, preferably greater than about 6%, by weight, based on theweight of components (II) and (III). Since these high molecular weightcompatibilizers can also be used as the high molecular weight,isocyanate-reactive component (II), they may be used to replace up to100% of component (II) or can be used in combination with other highmolecular weight, isocyanate-reactive components which do not functionas compatibilizers.

Regardless of the molecular weight of the compatibilizer, it should beused in an amount which is sufficient to solubilize the zinc carboxylateso that when the internal mold release agent mixture (IV) is blendedwith components (II) and (III), the zinc carboxylate possesses improvedresistance to precipitation.

Polyisocyanates (I)

Suitable polyisocyanates which may be used as component (I) include anyof the aliphatic, cycloaliphatic, araliphatic and aromaticpolyisocyanates known in polyurethane chemistry, especially those whichare liquid at room temperature. Preferred are the aromaticpolyisocyanates, especially those polyisocyanates which are based on4,4'-diisocyanatodiphenylmethane (MDI) or its isomers. Suitablepolyisocyanates of this type also include the polyphenyl polymethylenepolyisocyanates which may be obtained by anilineformaldehydecondensation followed by phosgenation (crude MDI). Also preferred arethe derivatives of MDI, its isomers or crude MDI such as polyurethaneprepolymers, carbodiimides, allophanates, etc., particularly those whichare liquid at room temperature, and mixtures thereof.

Particularly preferred are the liquid polyisocyanates containingurethane groups prepared from MDI, its isomers or crude MDI, butespecially MDI such as those described in U.S. Pat. No. 3,644,457. Thesepolyisocyanates containing urethane groups may be prepared by reactingone mol of MDI with from about 0.05 to 0.3 mols of low molecular weightdiols or triols, preferably with polypropylene glycols having amolecular weight below 700. In addition to these mixtures ofpolyisocyanates and isocyanate-terminated prepolymers, thepolyisocyanates (I) also include the isocyanate-terminated prepolymersknown from polyurethane chemistry and disclosed in U.S. Pat. No.4,374,210. However, the viscosity of these prepolymers should becarefully monitored since excessively high viscosities may causeprocessing difficulties in conventional RIM apparatus.

The polyisocyanate (I) is used in a quantity which will provide anisocyanate index for the reaction mixture of about 70 to 130, preferablyabout 90 to 110. The isocyanate index is the quotient of the number ofisocyanate groups and the number of isocyanate-reactive groups incomponents (II), (III) and (IVb) multiplied by 100.

High Molecular Weight Isocyanate-Reactive Component (II)

Suitable high molecular polymers which may be used in accordance withthe present invention are polyfunctional isocyanate-reactive, preferablypolyhydroxy, polymers having molecular weights of from about 1800 to12,000, preferably from about 3,000 to 7,000, and havingisocyanate-reactive functionalities of from 2 to 8, preferably 2 to 4.Included among the high molecular weight isocyanate-reactive polymersare polyethers, polyesters, polythioethers, polyacetals, polycarbonatesor polyester amides. Preferred are the polyethers and polyesters, andthe polyethers are particularly preferred. The high molecular weightpolymers preferably contain hydroxy groups, but it is also within thescope of the present invention to use polymers wherein a portion or allof the hydroxyl groups are replaced by amino groups. In this regard,polyethers wherein at least a portion of the hydroxyl groups have beenconverted to amino groups are especially suitable.

Suitable polyethers which may be used in accordance with the presentinvention are those prepared by the polymerization of epoxides, such asethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran,styrene oxide and/or epichlorohydrin, either on their own, e.g. in thepresence of BF₃ or by a process of chemical addition of these epoxides,optionally as mixtures or successively, to starting components havingisocyanate-reactive hydrogen atoms such as water, ammonia, alcohols oramines. Examples of suitable starting compounds are well known andinclude ethylene glycol, propylene glycol-(1,3) or -(1,2), glycerine,trimethylol propane, 4,4'-dihydroxy-diphenyl propane, aniline,ethanolamine or ethylene diamine. Polyether polyols based on propyleneand/or ethylene oxide are particularly preferred according to thepresent invention.

If the polyether polyols are to be used directly in the moldingcompositions of the present invention, then it is generally preferred touse polyethers which contain predominant amounts of primary OH groups,i.e. up to about 90%, by weight, based on all of the OH groups presentin the polyether. However, when filling large molds it may be necessaryto use larger quantities of polyethers containing secondary OH groups toprovide sufficient time to completely fill the mold before the reactionmixture gels or solidifies as taught in U.S. Pat. No. 4,379,105, hereinincorporated by reference. If the hydroxyl groups of the polyether areto be converted to amino groups prior to being used in the moldingcompositions of the present invention, then it is preferred that thepolyethers contain predominantly secondary hydroxyl groups sincesecondary hydroxyl groups are easier to aminate than primary hydroxylgroups.

Other polyethers which are suitable are those which have been modifiedwith vinyl polymers, for example, by the polymerization of styreneand/or acrylonitrile in the presence of polyethers. In addition,polyether polyols which contain high molecular weight polyadducts orpolycondensates in finely dispersed form or in solution may be used.Such modified polyether polyols are obtained when polyaddition reactions(e.g., reactions between the polyisocyanates and amino functionalcompounds) or polycondensation reactions (e.g., between formaldehyde andphenols and/or amines) are directly carried out in situ in the polyetherpolyols.

High molecular weight isocyanate-reactive polymers other than thepolyethers are disclosed in U.S. Pat. No. 4,218,543, the entiredisclosure of which is herein incorporated by reference.

Chain Extenders (III)

Suitable chain extenders are the known low molecular weightisocyanate-reactive compounds and include aromatic polyamines,especially diamines, having molecular weights of less than about 800,preferably less than about 500.

Preferred chain extenders are the sterically hindered aromatic diamineswhich contain at least one linear or branched alkyl substituent in theortho-position to the first amino group and at least one, preferablytwo, linear or branched alkyl substituents containing from 1 to 3 carbonatoms in the ortho-position to a second amino group. These aromaticdiamines include 1-methyl-3,5-diethyl-2,4-diamino benzene,1-methyl-3,5-diethyl-2,6-diamino benzene, 1,3,5-trimethyl-2,4-diaminobenzene, 1,3,5-triethyl-2,4-diamino benzene,3,5,3',5'-tetraethyl-4,4'-diamino diphenylmethane,3,5,3',5'-tetraisopropyl-4,4'-diamino diphenylmethane,3,5-diethyl-3',5'-diisopropyl-4,4'-diamino diphenylmethane,3,3'-diethyl-5,5'-diisopropyl-4,4'-diamino diphenylmethane,1-methyl-2,6-diamino-3-isopropylbenzene and mixtures of the abovediamines. Most preferred are mixtures of1-methyl-3,5-diethyl-2,4-diamino benzene and1-methyl-3,5-diethyl-2,6-diamino benzene in a weight ratio between about50:50 to 85:15, preferably about 65:35 to 80:20.

In addition, aromatic polyamines may be used in admixture with thesterically hindered chain extenders and include, for example, 2,4- and2,6-diamino toluene, 2,4'- and/or 4,4'-diamino-diphenyl-methane, 1,2-and 1,4-phenylene diamine, naphthalene-1,5-diamine andtriphenylmethane-4,4',4"-triamine. The difunctional and polyfunctionalaromatic amine compounds may also exclusively or partly containsecondary amino groups such as 4,4'-di-(methylamino)-diphenylmethane or1-methyl-2-methylamino-4-amino-benzene. Liquid mixtures of polyphenylpolymethylene-polyamines, of the type obtained by condensing anilinewith formaldehyde, are also suitable. Generally, the nonstericallyhindered aromatic diamines and polyamines are too reactive to providesufficient processing time in a RIM system. Accordingly, these diaminesand polyamines should generally be used in combination with one or moreof the previously mentioned sterically hindered diamines.

The chain extender (III) is used in quantities of about 5 to 50%,preferably about 8 to 30% and most preferably about 12 to 26%, byweight, based on the weight of high molecular weight isocyanate-reactivecomponent (II).

Other additives which may be used in the molding compositions of thepresent invention include catalysts, especially tin (II) salts ofcarboxylic acids, dialkyl tin salts of carboxylic acids, dialkyl tinmercaptides, dialkyl tin dithioesters and tertiary amines. Preferredamong these catalysts are dibutyl tin dilaurate and1,4-diaza-bicyclo-(2,2,2)-octane (triethylene diamine), especiallymixtures of these catalysts. The catalysts are generally used in amountsof about 0.01 to 10%, preferably about 0.05 to 2.0%, based on the weightof high molecular weight isocyanate-reactive component (II).

It is also possible to use surface-active additives such as emulsifiersand foam stabilizers. Examples include N-stearyl-N',N'-bis-hydroxyethylurea, oleyl polyoxyethylene amide, stearyl diethanol amide, isostearyldiethanol amide, polyoxyethylene glycol mono-oleate, an ester ofpentaerythritol, adipic acid and oleic acid, a hydroxy ethyl imidazolederivative of oleic acid, N-stearyl propylene diamine and the sodiumsalts of castor oil sulfonates or of fatty acids. Alkali metal orammonium salts of sulfonic acid, such as dodecyl benzene sulfonic acidor dinaphthyl methane disulfonic acid and also fatty acids such asricinoleic acid or polymeric fatty acids may also be used assurface-active additives.

Suitable foam stabilizers are, for example, water-soluble polyethersiloxanes. The structure of these compounds is generally such that acopolymer of ethylene oxide and propylene oxide is attached to apolydimethyl siloxane radical. Such foam stabilizers are described inU.S. Pat. No. 2,764,565.

In addition to the catalysts and surface-active agents, other additiveswhich may be used in the molding compositions of the present inventioninclude the known blowing agents, cell regulators, flame retardantagents, plasticizers, dyes, fillers and reinforcing agents such as glassor carbon fibers.

The compositions according to the present invention may be molded usingconventional RIM processing techniques. In general, two separate streamsare intimately mixed and subsequently injected into a suitable moldalthough it is possible to use more than two streams. The first streamcontains the polyisocyanate component (I), while the second streamcontains the high molecular weight isocyanate-reactive component (II),the chain extender (III), the internal mold release agent mixture (IV)and any other additive which is to be included.

In preparing the internal mold release mixture according to the presentinvention, it is recommended to add the solid zinc carboxylate (IVa) tothe compatibilizer (IVb). It is also recommended to heat this mixture atelevated temperatures (about 80°-120° C.) with continual or occasionalstirring until a clear solution is obtained. The solution may then becooled to ambient temperature or, if necessary to maintain liquidity,kept at slightly elevated temperature until use.

In order to provide improved resistance to precipitation of the zinccarboxylate, it is preferred that the mold release mixture of component(IV) contain less than about 50% by weight of zinc carboxylate and morethan about 50% by weight of the nitrogen-containing compatibilizer whenpresent in concentrated form, i.e. prior to admixture with the highmolecular weight isocyanate-reactive component. However, this limitationis not essential for providing mold release properties, but does provideincreased storage stability for the mold release concentrate. The moldrelease concentrate may, however, contain all or a portion of the chainextender.

Prior to use, the mold release concentrate may be blended with theremainder of the isocyanate-reactive components of the second stream andagitated briefly to ensure homogeneity. If used, the reinforcing agentmay be added to the resin blend at this time.

EXAMPLES

Experimental formulations were evaluated on a Cincinnati-MilacronRIMM-90 reinforced RIM machine with a Chevrolet Monte Carlo front fasciamold. Performance of experimental candidates was rated according to theease of release from the prepared mold surface; the number of releasesbefore part sticking, tearing or distortion; the part toughness atdemold (green strength); and the flowability indicated by the presenceof absence of flowlines, visible density gradients or unfilled areas ofthe part.

Reinforced RIM evaluations were conducted on the same machine withsufficient amounts of the desired reinforcement (Owens-Corning FiberglasNo. 737 1/32" milled glass fiber, except for Examples 45-48 which useglass flake reinforcement) dispersed in the isocyanate-reactive mixtureso that the final part (once the isocyanate-reactive mixture has beencombined with the proper amount of isocyanate) will contain the desiredreinforcement content.

Procedure for Preparation of Internal Mold Release Agent Mixture

Eight parts of zinc stearate were added to 8 parts of polyetherpolyamine I in a five-gallon steel can. The can was placed in a 100° C.oven and stirred with a rod every 15 minutes. After two hours, themixture was a clear solution which remained clear upon cooling toambient temperature.

Procedure for Preparation of Resin Blend For Machine Evaluation

Four parts of the 1:1 solution of zinc stearate/polyether polyamine Iwas added to 96 parts of a resin blend of 79.3 parts of polyether polyolA, 16.5 parts of chain extender C (DETDA), 0.1 parts of tin catalystDBTDL and 0.1 parts of amine catalyst Dabco 33LV. After 15 minutes ofagitation with a mechanical stirrer a clear amber resin blend wasobtained and loaded into the machine for evaluation.

Procedure for Mold Preparation

Prior to evaluating the RIM formulation, the mold surface was cleaned ofpossible residue by wiping with hot water until the sudsy residuedisappeared. The surface was then wiped with a commercial mold cleaner(Chemtrend MC-201-B) until any visible urethane or other residues wereremoved. The mold surface was then again wiped with hot water andsubsequently with a dry cloth. A commercial soap-type external moldrelease agent (e.g. Chemtrend RCTW 2006 or Frekote RIMLEASE 14) was thenlightly sprayed onto all release surfaces of the mold. The release agentfilm was then gently buffed in by hand with a soft cloth and then themold was again lightly sprayed with the release agent.

The mold was then ready for evaluation of the internal releaseformulation. The effectiveness of the formulation was judged by the easeof release, the flowability and toughness at demold, green strength, andthe number of releases obtained before part removal became difficult orthe parts became distorted or damaged at demold because of the adherenceof the part to the mold surface.

All of the experiments set forth in the Tables were conducted using thepreviously described procedures.

The invention is further illustrated, but is not intended to be limitedby the following examples in which all parts and percentages are byweight unless otherwise specified.

Description of Materials

Polyol A--a glycerine-initiated poly(oxyalkylene)polyether triol havinga hydroxyl number of 28 and containing about 82.5% propylene oxide andtipped with about 17.5% ethylene oxide.

Polyol B--a glycerine-initiated poly(oxyalkylene)polyether triol havinga hydroxyl number of 28 and containing about 86% propylene oxide andtipped with about 14% ethylene oxide.

Chain Extender C--a commercial preparation of diethyl toluene diamine(DETDA) which is an isomeric mixture of 1-methyl-3,5-diethyl-2,4-diaminobenzene and 1-methyl-3,5-diethyl-2,6-diamino benzene in a ratio ofbetween 65:35 and 80:20.

Crosslinker D--an amine-initiated poly(oxyalkylene)polyether tetrolhaving an hydroxyl number of about 630 and obtained by the addition ofabout 5 moles of propylene oxide to one mole of ethylene diamine.

Chain Extender E--a triethyl phenylene diamine (TEMPDA) which ispredominantly (˜95%) 1,3,5-triethyl-2,4-diamino benzene.

Polyisocyanate F--4,4'-diphenylmethane diisocyanate which has beenliquified by reaction in a molar ratio of about 5:1 with tripropyleneglycol to give a liquid product having an NCO content of about 23% and aviscosity at 25° C. of 725±175 cps.

Polyisocyanate G--a prepolymer prepared by the addition of 8 parts of apolyester derived from the reaction of oleic acid, adipic acid, andpentaerythritol (in a molar ratio of 6:1:3) to 100 parts ofpolyisocyanate F, the prepolymer having an NCO content of about 20.5%and a viscosity of 900±100 cps.

Polyisocyanate H--a prepolymer prepared by the addition of 8 parts offatty surface active agent 0 to 100 parts of polyisocyanate F, theprepolymer having an NCO content of about 19.9% and a viscosity at 25°C. of about 1200±200 cps.

Tin Catalyst I--dibutyl tin dilaurate, supplied as Thermolite 12 by M &T Chemicals or as Fomrex SUL-4 by Witco.

Tin Catalyst II--dimethyl tin dilaurate, supplied as Fomrez UL-28 byWitco.

Amine Catalyst--triethylene diamine, supplied as a 33% solution in aglycol carrier, as DABCO 33LV by Air Products or as Thancat TD-33 byTexaco.

Polyether Polyamine I--an approximately 400 MW difunctional primaryamine terminated polyether supplied by Texaco as Jeffamine D-400.

Polyether Polyamine J--an approximately 5000 MW trifunctional primaryamine terminated polyether supplied by Texaco as Jeffamine T-5000.

Fatty Surface-Active Agent K--a commercial preparation of anN,N-diethanol amide of isostearic acid, supplied as Schercomid SI byScher Chem Company.

Fatty Surface-Active Agent L--a commercial preparation of anN,N-diethanol amide of stearic acid, supplied as Monamid 718 by MonaIndustries.

Fatty Surface-Active Agent M--a commercial preparation of anhydroxyethyl imidazoline derivative of oleic acid, supplied asMonazoline O by Mona Industries.

Fatty Surface-Active Agent N--an experimental preparation of a fattyester obtained by condensation of ricinoleic acid with hexanediol havinga hydroxyl number of 33±5 and a viscosity at 25° C. of 1250±200 cps.

Fatty Surface-Active Agent O--a polyoxyethylene glycol ester of oleicacid, supplied as PEG 200 Monooleate by Stepan Chemical.

Surfactant P--a commercial silicone surfactant supplied as L-5430 byUnion Carbide.

The components used in the RIM formulations and the results of theexperimental runs are set forth in the following Tables.

The following are the typical conditions for processing the unreinforcedformulations on the Cincinnati-Milacron RIMM-90 for the Monte Carlofascia. Adjustments in these conditions are required for the evaluationscontaining a reinforcing agent.

    ______________________________________                                        Mixhead Type          50/90                                                   Weight Ratio, polyisocyanate/resin blend                                                            49/100                                                  Injection Rate, pounds per second                                                                   5.0                                                     Part Weight, pound    8.1                                                     Mold Temperature, °F.                                                                         150                                                    Resin Blend, specific gravity, g/cc                                                                  0.75                                                   Material Temperature, °F.                                              Polyisocyanate Component                                                                             95                                                     Resin Component        100                                                    Mix Pressures, psi                                                            Polyisocyanate Component                                                                            1575                                                    Resin Blend Component 1500                                                    Mold Basecoat         Soap-type                                                                     external release agent                                  Demold time, seconds   30                                                     ______________________________________                                    

    __________________________________________________________________________               Example                                                                       1       2       3       4       5                                             (Comparison)                                                                          (Comparison)                                                                          (Comparison)                                                                          (Comparison)                                                                          (Comparison)                       __________________________________________________________________________    Polyol, parts                                                                            A, 82.1 B, 82.1 A, 76.1 A, 65.0 B, 71.7                            Crosslinker D                                                                            --      --      --      --      2.0                                Chain Extender C                                                                         17.7    17.7    17.7    16.7    18.0                               Polyamine I                                                                              --      --      --      --      --                                 Polyamine J                                                                              --      --      --      10.0    --                                 Tin Catalyst I                                                                           0.1     0.1     0.1     0.2     0.2                                Amine Catalyst                                                                           0.1     0.1     0.1     0.1     0.1                                Metallic Carboxylate,                                                                    --      --      --      --      --                                 parts                                                                         Surface-active Agent,                                                                    --      --      N, 7.0  N, 7.0  K, 8.0                             parts                                                                         Polyisocyanate                                                                           F       F       F       G       H                                  Green Strength                                                                           Excellent                                                                             Good    Fair    Fair    Excellent                          @ Demold Time                                                                            @ 30 sec.                                                                             @ 30 sec.                                                                             @ 30 sec.                                                                             @ 40 sec.                                                                             @ 30 sec.                          Number Releases                                                                           6       6*       7**    8       4                                 Flowability                                                                              Good    Good    Good    Good    Good                               Milled Glass                                                                             --      --      --      --      --                                 Fiber Reinforcement                                                           __________________________________________________________________________               Example                                                                       6       7       8       9       10                                            (Comparison)                                                                          (Comparison)                                                                          (Comparison)                                                                          (Comparison)                                                                          (Comparison)                       __________________________________________________________________________    Polyol, parts                                                                            A, 81.8 A, 78.7 B, 79.0 A, 79.3 A, 77.25                           Crosslinker D                                                                            1.0     1.0     1.0     2.0     2.0                                Chain Extender C                                                                         17.0    18.0    17.8    16.5    16.5                               Polyamine I                                                                              --      --      --      --      --                                 Polyamine J                                                                              --      --      --      --      --                                 Tin Catalyst I                                                                           0.1     0.2     0.1     0.1      0.15                              Amine Catalyst                                                                           0.1     0.1     0.1     0.1     0.1                                Metallic Carboxylate,                                                                    --      --      --      Magnesium                                                                             Magnesium                          parts                              Ricinoleate 1.0                                                                       Ricinoleate 2.0                    Surface-active Agent,                                                                    --      O, 2.0  O, 2.0  K, 1.0  K, 2.0                             parts                                                                         Polyisocyanate                                                                           H       H       G       F       F                                  Green Strength                                                                           Good @  Fair @  Good @  Good @  Fair @                             @ Demold Time                                                                            30 sec. 30 sec. 30 sec. 30 sec. 30 sec.                            Number Releases                                                                           5      11       2       4       3                                 Flowability                                                                              Good    Good    Good    Good    Good                               Milled Glass                                                                             --      --      --      --      --                                 Fiber Reinforcement                                                           __________________________________________________________________________               Example                                                                       11      12      13      14      15                                 __________________________________________________________________________    Polyol, parts                                                                            A, 79.1 A, 77.3 A, 79.4 A, 78.1 A, 68.1                            Crosslinker D                                                                            2.0     2.0     1.0     1.0     --                                 Chain Extender C                                                                         16.5    16.5    16.7    16.7    17.7                               Polyamine I                                                                              --      --      --      --      --                                 Polyamine J                                                                              --      --      --      --      10.0                               Tin Catalyst I                                                                           0.1     0.1     0.1     0.1     0.1                                Amine Catalyst                                                                           0.1     0.1     0.1     0.1     0.1                                Metallic Carboxylate,                                                                    Zinc Oleate                                                                           Zinc Oleate                                                                           Zinc Oleate                                                                           Zinc Stearate                                                                         Zinc Stearate                      parts      1.1     2.0     1.5     2.0     2.0                                Surface-active Agent,                                                                    K, 1.1  K, 2.0  K, 1.2  K, 2.0  K, 2.0                             parts                                                                         Polyisocyanate                                                                           F       F       F       F       F                                  Green Strength                                                                           Fair @  Fair @  Very Good @                                                                           Good @  Excellent                          @ Demold Time                                                                            30 sec. 30 sec. 30 sec. 30 sec. 30 sec.                            Number Releases                                                                           7       7      20      40      19                                 Flowability                                                                              Fair    Fair    Good    Good    Good                               Milled Glass                                                                             --      --      --      --      --                                 Fiber Reinforcement                                                           __________________________________________________________________________               Example                                                                       16      17      18      19      20                                 __________________________________________________________________________    Polyol, parts                                                                            A, 72.9 A, 52.6 A, 77.8 A, 78.3 A, 75.3                            Crosslinker D                                                                            --      --      1.0     1.0     --                                 Chain Extender C                                                                         15.4    16.7    17.0    16.5    16.5                               Polyamine I                                                                              7.7     --      --      --      4.0                                Polyamine J                                                                              --      22.0    --      --      --                                 Tin Catalyst I                                                                           0.1     0.1     0.1     0.1     0.1                                Amine Catalyst                                                                           0.1     0.1     0.1     0.1     0.1                                Metallic Carboxylate,                                                                    Zinc Stearate                                                                         Zinc Stearate                                                                         Zinc Stearate                                                                         Zinc Stearate                                                                         Zinc Stearate                      parts      1.9     1.5     2.0     2.0     2.0                                Surface-active Agent,                                                                    K, 1.9  N, 7.0  K, 2.0  K, 2.0  L, 2.0                             parts                                                                         Polyisocyanate                                                                           F       F       F       F       F                                  Green Strength                                                                           Fair @  Good @  Good @  Good @  Fair @                             @ Demold Time                                                                            40 sec. 30 sec. 30 sec. 30 sec. 30 sec.                            Number Releases                                                                          25      45      20      28      60                                 Flowability                                                                              Good    Fair; Flow                                                                            Good    Good    Fair; Sl. Flow                                        Lines & Visible         Lines & Dense                                         Dense Area              Area                               Milled Glass                                                                             --       15%    --      --      --                                 Fiber Reinforcement                                                           __________________________________________________________________________               Example                                                                       21      22      23      24      25                                 __________________________________________________________________________    Polyol, parts                                                                            A, 77.4 A, 77.2 A, 77.2 A, 76.1 A, 77.3                            Crosslinker D                                                                            --      --      --      1.0     --                                 Chain Extender C                                                                         16.5    16.5    16.5    16.3    16.5                               Polyamine I                                                                              2.2     2.0     2.0     2.0     2.0                                Polyamine J                                                                              --      --      --      --      --                                 Tin Catalyst I                                                                           0.1     0.1     0.1     0.5     0.1                                Amine Catalyst                                                                           0.1     0.1     0.1     0.1     0.1                                Metallic Carboxylate,                                                                    Zinc Stearate                                                                         Zinc Stearate                                                                         Zinc Stearate                                                                         Iron Stearate                                                                         Zinc-12-Hy-                        parts      2.0     2.0     2.0     2.0     droxy Stearate,                                                               2.0                                Surface-active Agent,                                                                    L, 1.7  L, 2.1  K, 2.1  K, 2.0  K, 2.0                             parts                                                                         Polyisocyanate                                                                           F       F       F       F       F                                  Green Strength                                                                           Good @  Fair @  Good @  Fair @  Good @                             @ Demold Time                                                                            30 sec. 30 sec. 30 sec. 30 sec. 30 sec.                            Number Releases                                                                          30      46      44      10       5                                 Flowability                                                                              Sl. Dense                                                                             Good    Good    Good    Sl. Dense                                     Area                            Area                               Milled Glass                                                                             --      --      --      --      --                                 Fiber Reinforcement                                                           __________________________________________________________________________               Example                                                                       26      27      28      29      30                                 __________________________________________________________________________    Polyol, parts                                                                            A, 77.3 A, 77.3 A, 75.3 A, 75.8 A, 77.3                            Crosslinker D                                                                            --      --      --      --      --                                 Chain Extender C                                                                         16.5    16.5    16.5    16.0    16.5                               Polyamine I                                                                              2.0     2.0     4.0     4.0     2.0                                Polyamine J                                                                              --      --      --      --      --                                 Tin Catalyst I                                                                           0.1     0.1     0.1     0.1     0.1                                Amine Catalyst                                                                           0.1     0.1     0.1     0.1     0.1                                Metallic Carboxylate,                                                                    Zinc Laurate                                                                          Iron Stearate                                                                         Zinc Stearate                                                                         Zinc Stearate                                                                         Zinc Stearate                      parts      2.0     2.0     2.0     2.0     2.0                                Surface-active Agent,                                                                    K, 2.0  M, 2.0  K, 2.0  K, 2.0  K, 2.0                             parts                                                                         Polyisocyanate                                                                           F       F       F       F       F                                  Green Strength                                                                           Good @  Good @  Good @  Good @  Good @                             @ Demold Time                                                                            30 sec. 30 sec. 30 sec. 30 sec. 30 sec.                            Number Releases                                                                          13       5      44      26      25                                 Flowability                                                                              Good    Good    Good    Sl. Flow Lines                                                                        Good                               Milled Glass                                                                             --      --      --      --       15%                               Fiber Reinforcement                                                           __________________________________________________________________________               Example                                                                       31      32      33      34      35                                 __________________________________________________________________________    Polyol, parts                                                                            B, 77.3 B, 77.3 A, 77.3 A, 77.3 A, 77.3                            Crosslinker D                                                                            --      --      --      --      --                                 Chain Extender C                                                                         16.5    16.5    16.5    16.5    16.5                               Polyamine I                                                                              2.0     2.0     2.0     2.0     2.0                                Polyamine J                                                                              --      --      --      --      --                                 Tin Catalyst I                                                                           0.1     0.1     0.1     0.1     0.1                                Amine Catalyst                                                                           0.1     0.1     0.1     0.1     0.1                                Metallic Carboxylate,                                                                    Zinc Stearate                                                                         Zinc Stearate                                                                         Zinc Stearate                                                                         Zinc Stearate                                                                         Zinc Stearate                      parts      2.0     2.0     2.0     2.0     2.0                                Surface-active Agent,                                                                    K, 2.0  K, 2.0  K, 2.0  L, 2.0  L, 2.0                             parts                                                                         Polyisocyanate                                                                           F       F       F       F       F                                  Green Strength                                                                           Fair @  Good @  Good @  Good @  Very Good @                        @ Demold Time                                                                            30 sec. 30 sec. 30 sec. 30 sec. 30 sec.                            Number Releases                                                                           6      16      22      42      53                                 Flowability                                                                              Sl. Dense                                                                             Good    Fair; Sl.                                                                             Good    Good                                          Area            Flow Lines                                         Milled Glass                                                                              15%    --      --      --       15%                               Fiber Reinforcement                                                           __________________________________________________________________________               Example                                                                       36      37      38      39      40                                 __________________________________________________________________________    Polyol, parts                                                                            A, 77.3 A, 79.3 B, 78.4 A, 79.3 A, 78.85                           Crosslinker D                                                                            --      --      1.0     --      --                                 Chain Extender C                                                                         16.5    16.5    16.3    16.5    16.4                               Polyamine I                                                                              4.0     2.0     2.0     2.0     2.0                                Polyamine J                                                                              --      --      --      --      --                                 Tin Catalyst I                                                                           0.1     0.1     0.2     0.1      0.15                              Amine Catalyst                                                                           0.1     0.1     0.1     0.1     0.1                                Metallic Carboxylate,                                                                    Zinc Stearate                                                                         Zinc Stearate                                                                         Zinc Stearate                                                                         Zinc Stearate                                                                         Zinc Stearate                      parts      2.0     2.0     2.0     2.0     2.0                                Surface-active Agent,                                                                    --      --      --      --      M, 0.5                             parts                                                                         Polyisocyanate                                                                           F       F       F       F       F                                  Green Strength                                                                           Good @  Poor @  V. Good @                                                                             Fair @  Good @                             @ Demold Time                                                                            30 sec. 30 sec. 30 sec. 30 sec. 30 sec.                            Number Releases                                                                          35       8      25      21       3                                 Flowability                                                                              Good    Good    Good    Good    Fair                               Milled Glass                                                                             --      --      --       15%     15%                               Fiber Reinforcement                                                           __________________________________________________________________________                 Example                                                                       41       42        43        44                                  __________________________________________________________________________    Polyol, parts                                                                              B, 77.25 A, 77.3   A, 77.3   A, 73.8                             Crosslinker D                                                                              2.0      2.0       2.0       2.0                                 Chain Extender C                                                                           16.5     16.5      16.5      20.0                                Polyamine I  2.0      2.0       2.0       2.0                                 Polyamine J  --       --        --        --                                  Tin Catalyst I                                                                              0.15    0.1       0.1       0.1                                 Amine Catalyst                                                                             0.1      0.1       0.1       0.1                                 Metallic Carboxylate,                                                                      Zinc Stearate                                                                          Zinc Stearate                                                                           Zinc Stearate                                                                           Zinc Stearate                       parts        2.0      2.0       2.0       2.0                                 Surface-active Agent,                                                                      --       --        --        --                                  parts                                                                         Polyisocyanate                                                                             F        F         F         F                                   Green Strength                                                                             Good @ 30 sec.                                                                         V. Good @ 30 sec.                                                                       V. Good @ 30 sec.                                                                       Fair @ 30 sec.                      @ Demold Time                                                                 Number Releases                                                                            30       30        88        30                                  Flowability  Good     Good      Good      Good                                Milled Glass --        15%      --         15%                                Fiber Reinforcement                                                           __________________________________________________________________________               Example                                                                       45      46      47      48      49                                 __________________________________________________________________________    Polyol, parts                                                                            A, 71.8 A, 70.8 A, 66.8 A, 66.8 B, 84.3                            Crosslinker D                                                                            2.0     3.0     3.0     1.0     2.0                                Chain Extender E                                                                         --      23.0    27.0    27.0    --                                 Chain Extender C                                                                         21.0    --      --      --      10.5                               Polyamine I                                                                              2.0     --      --      2.0     2.0                                Tin Catalyst I                                                                            0.05    0.05    0.05    0.05   0.1                                Tin Catalyst II                                                                           0.05    0.05    0.05    0.05   --                                 Amine Catalyst                                                                           0.1     0.1     0.1     0.1     0.1                                Metallic Carboxylate,                                                                    Zinc stearate                                                                         Zinc stearate                                                                         Zinc stearate                                                                         Zinc stearate                                                                         Zinc stearate                      parts      2.0     2.0     2.0     2.0     2.0                                Surfactant P                                                                             1.0     1.0     1.0     1.0     --                                 Polyisocyanate                                                                           F       F       F       F       F                                  Flowability                                                                              Good    Good    Good    Good    Good                               Glass Flake                                                                              20      20      15      15      --                                 Reinforcement                                                                 % in final part                                                               Carbon black paste***                                                                    --      --      --      --      4.0                                __________________________________________________________________________     *Average of 4 runs                                                            **Average of 3 runs                                                           ***DR2-205 as a dispersion in a polyether polyol from Plasticolors       

When Chain Extender E was used in place of Chain Extender C in Examples46-48, the ease of release of the molded parts from the mold wasunchanged from Example 45; however, the total number of releases werenot determined.

In Example 49 the composition was introduced into a mold having asilicone polymer surface and containing a glass insert. When released,the molded part adhered to the glass, but not to the mold surface. Thetotal number of releases were not determined.

Although the invention has been described in detail in the foregoing forthe purpose of illustration, it is to be understood that such detail issolely for that purpose and that variations can be made therein by thoseskilled in the art without departing from the spirit and scope of theinvention except as it may be limited by the claims.

What is claimed is:
 1. A process for the production of optionallycellular, polyurethane elastomer moldings by reacting a reaction mixturecomprising(I) a polyisocyanate, (II) an isocyanate-reactive polymerhaving a molecular weight of about 1,800 to 12,000 (III) about 5 to 50%by weight, based on the weight of component (II) of a chain-extendercomprising a sterically hindered aromatic diamine and (IV) an internalmold release agent mixture comprising(a) about 0.5 to 10% by weight,based on the weight of components (II) and (III) of a zinc carboxylatecontaining 8 to 24 carbon atoms per carboxylate group and (b) acompatibilizer comprising an amine- or hydroxyl-terminated,amine-initiated polyether in an amount sufficient to solubilize the zinccarboxylate so that when the internal mold release agent mixture is inadmixture with components (II) and (III), the zinc carboxylate possessesimproved resistance to precipitation,said reaction mixture beingprocessed as a one-shot system by the RIM process at an isocyanate indexof about 70 to
 130. 2. The process of claim 1 wherein saidamine-initiated polyether contains the grouping --N--C--C--N--.
 3. Theprocess of claim 2 wherein said zinc carboxylate comprises zincstearate.
 4. The process of claim 2 wherein said amine-initiatedpolyether is an amine-initiated polyether polyol.
 5. The process ofclaim 1 wherein said compatibilizer additionally comprises anamine-terminated polyether.
 6. A process for the production ofoptionally cellular, polyurethane elastomer moldings by reacting areaction mixture comprising(I) a polyisocyanate which is liquid at roomtemperature, (II) a polyether polyol having a molecular weight of about3000 to 7000, (III) about 5 to 50% by weight, based on the weight ofcomponent (II) of a chain extender comprising a member selected from thegroup consisting of 1-methyl-3,5-diethyl-2,4-diamino benzene,1-methyl-3,5-diethyl-2,6-diamino benzene, 1,3,5-triethyl-2,4-diaminobenzene and (IV) an internal mold release agent mixture comprising(a)about 0.5 to 10% by weight, based on the weight of components (II) and(III) of zinc stearate and (b) a compatibilizer comprising anamine-initiated polyether polyol containing the grouping --N--C--C--N--in an amount of about 0.5 to 10% by weight, based on the weight ofcomponents (II) and (III), to solubilize the zinc stearate so that whenthe internal mold release agent mixture is in admixture with components(II) and (III), the zinc stearate possesses improved resistance toprecipitation,said reaction mixture being processed as a one-shot systemby the RIM process at an isocyanate index of about 70 to
 130. 7. Theprocess of claim 6 wherein said compatibilizer additionally comprises anamine-terminated polyether.
 8. An isocyanate-reactive composition foruse in a RIM process which comprises:(II) an isocyanate-reactive polymerhaving a molecular weight of about 1800 to 12,000, (III) about 5 to 50%by weight, based on the weight of component (II) of a chain extendercomprising a sterically hindered aromatic diamine and (IV) an internalmold release agent mixture comprising(a) about 0.5 to 10% by weight,based on the weight of components (II) and (III) of a zinc carboxylatecontaining 8 to 24 carbon atoms per carboxylate group and (b) acompatibilizer comprising an amine- or hydroxyl-terminated,amine-initiated polyether in an amount sufficient to solubilize the zinccarboxylate that when the internal mold release agent mixture is inadmixture with components (II) and (III), the zinc carboxylate possessesimproved resistance to precipitation.
 9. The process of claim 8 whereinsaid amine-initiated polyether contains the grouping --N--C--C--N--. 10.The isocyanate-reactive composition of claim 9 wherein said zinccarboxylate comprises zinc stearate.
 11. The isocyanate-reactivecomposition of claim 9 wherein said amine-initiated polyether is anamine-initiated polyether polyol.
 12. The isocyanate-reactivecomposition of claim 8 wherein said compatibilizer additionallycomprises an amine-terminated polyether.
 13. An internal mold releaseagent composition comprising(a) zinc stearate and (b) a compatibilizercomprising an amine- or hydroxyl-terminated, amine-initiated polyetherpolyol.
 14. The internal mold release agent composition of claim 13wherein said amine-initiated polyether contains the grouping--N--C--C--N--.
 15. The internal mold release agent composition of claim13 wherein said zinc carboxylate is present in an amount of less than50% by weight based on the weight of components (a) and (b).
 16. Theinternal mold release agent composition of claim 13 wherein saidcompatibilizer additionally comprises an amine-terminated polyether. 17.The internal mold release agent composition of claim 14 wherein saidamine-initiated polyether is an amine-initiated polyether polyol.